Fuel feeding device



Oct. 10, 1967 a. WALKER 3,346,243

FUEL FEEDING DEVICE Filed Jan. 25, 1965 4 Sheets-Sheet 1 Oct. 10, 1967 B. WALKER 3,346,243

FUEL FEEDING DEVI CE Filed Jan. 25, 1965 4 Sheets-Sheet 2 INVENTOR.

Oct. 10, 1967 B. WALKER 3,346,243

- Y FUEL FEEDING DEVICE Filed Jan. 25, 1965 4 Sheets-Sheet 5 INVENTOR.

Oct. 10, 1967 B. WALKER 3,346,243

I FUEL FEEDING DEVICE Filed Jan. 25, 1965 4 Sheets-Sheet 4 TOT/N m K5 MA IV/FOLD 73 THROTTLE 50 CLOSED VA 1. v5

OPENED- IN VENTOR.

United States Patent O 3,346,243 FUEL FEEDlNG DEVICE Brooks Walker, 1280 Columbus Ave., San Francisco, Calif. 94133 Filed Jan. 25, 1965, Ser. No. 427,649 4 Claims. (Cl. 261-41) This invention pertains to an improved carburetor.

One object of the invention is to reduce the unburned hydrocarbons in the exhaust, primarily by providing an improved idling mixture and an improved method of cutting off the fuel to idle when decelerating above a predetermined speed.

Another object of this invention is to support a mechanism for accomplishing these results entirely on the carburetor.

The desired results may be obtained by two motors or two enclosures with diaphragms-one larger diaphragm to shut off the fuel to idle by a power device plug type Valve in the fuel to idle circuit, and a second smaller diaphragm operated by the higher pressure from a Pitot pickup. For example, the Pitot tube may be located at the perimeter of a Water pump rotor and may be connected to one side of a large diaphragm and the lower pressure from the intake of the water pump may act on the other side of the large diaphragm. The two diaphragms eliminate the need for a stuffing box on the shaft from the large diaphragm to the valve to control the flow of suction from the manifold to the first motor or enclosure with a diaphragm that shuts off the fuel to idle on high speed decelerations.

Another feature is the use of the double diaphragm (one large and one small) on the water-pump-pressureoperated governor motor or speed senser with the pressure from the Pitot pick up acting on the side of the larger diaphragm away from the smaller diaphragm and the pressure from the intake of the water pump acting between the large diaphragm and the small diaphragm so that as the pressure in the radiator due to increased temperature and the pressure cap is high at high temperatures of the motor the pressure operated speed sensing diaphragms will shift at lower speeds than at lower engine temperature operation. This is due to the higher radiator water pressure acting on both sides of the larger diaphragm and on only one side of the smaller diaphragm to buck the spring that opposes the action of the large diaphragm in moving under the action of the liquid pressure from the Pitot pick up. This motion of the large diaphragm under the pressure from the Pitot pick up operates the associated vacuum controlling valve. This valve in turn operates the motor or diaphragm operated valve to cut off the fuel to idle. The circuit that controls the suction to the valve that controls the fuel to idle shut E also includes a valve which opens when the throttle is closed, two open the lines from the intake manifold to apply engine manifold suction to the speed sensing governor only when the throttle is closed.

Another feature is a snap action of the speed sensing device so that the idle fuel will either be on or off and not linger in the transition.

Another feature is the mixing of the fuel to idle with the air to idle and introduce it into the manifold near the center of the passage on the engine side of the carburetor butterfly which is preferably closed at idle and decelerating conditions.

An object of this invention is the better mixing of fuel and air to idle and the control of the idle fuel to shut it off on high speed decelerations in a simple better way than has been available before and in a compact package that will be better available for converting exiting vehicle motor to comply with antismog requirements than other devices.

3,346,243 Patented Oct. 10, 1967 Another feature is the use of a valve to open the line of suction from the intake manifold to the speed sensing valve rather than bleed valves as used in the Mallory, No. 2,420,786 patent, dated May 20, 1947, entitled De- Gasser for an Internal Combustion Engine. The water pump operated speed senser has been shown in my US. patent application, Serial No. 317,403, dated October 16, 1963, entitled Speed Sensing Device, and now Patent No. 3,204,620, but such application does not shown the snap action shown herein or the double diaphragm that eliminates the stuffing box and gives action at a lower engine speed range at high engine temperatures and increased radiator pressures compared to the speed range of action at low temperature engine operating conditions.

Another feature is the use of the bent rod control from the throttle to the anti-percolator valve to operate the throttle closed valve in order to reduce the mechanism and better support the valve on the carburetor. The valve combination used to control fluid flow to the device that shuts off the fuel to idle could be used with a large variety of different types of controls to shut off the fuel to idle, such as a butterfly under the throttle butterfly as shown in US. Patent No. 2,395,748, by Mallory, dated February 26, 1946, entitled De-Gasser for Internal Combustion Engine, or any other suitable type of shut off of the fuel to idle all within the scope of this invention.

Other features of this invention will be pointed out in the accompanying specification and claims.

I have illustrated my invention by way of example in the accompanying drawings, in which:

FIG. 1 is a top plan view of a carburetor embodying one form of the invention, with some parts removed.

FIG. 2 is a side elevation of the carburetor shown in FIG. lwith some parts added.

FIG, 3 'is a plan view partly in section of the sandwich between the main body of the carburetor shown in FIGS. 1 and 2 and the engine to which it is attached.

FIG. 4 is a sectional view of the carburetor shown in FIGS. 1 and 2.

FIG. 5 is a horizontal elevation section taken along the line 5-5 of FIG. 4.

FIG. 6 is a side elevation partly cut .away of portions of the carburetor and its controls in somewhat diagrammatic form, some of the partsbeing shown in a form that is modified with respect to FIGS. 1-5.

In all figures like numerals of reference refer to corresponding parts.

In FIGS. 1 through 5, I have shown a carburetor 10 with a choke valve 11, a main induction throat 12, and a main jet 13. Main throttle valve 14 is mounted on and controlled by a throttle shaft 15.

A carburetor fuel bowl or float chamber 20 contains fuel 21 on which a float 22 floats. A passage 23 leads from the lower portion of the fuel bowl 20 to a horizontal passage 24. A bleed 25 admits air to the passage 24 to enable passage of idle air to the fuel and to prevent fuel from syphoning over when the vehicle is stopped and to prevent it flooding the carburetor while the engine is stopped. A plug valve 26 is mounted on a stem 27 in the passage 24 and controls the flow of a rich mixture of air and idle fuel from the passage 24 into a vertical passage 30. When the valve 26 is moved to the position shown in FIG. 4 idle fuel is cut off. When moved further to the right, idle fuel'can pass.

The passage 30 leads past a transfer port 31, which may be a thin slot or group of orifices and may be used to get a smooth transition from the idle condition 40 where the throttle valve is partly open, this being an expedient found on' many carburetors. The passage 30 terminates shortly beyond a port 32where a needle valve 33 regulates passage into a chamber 34, the valve 3 3 being adjusted by a threaded valve 35 that is normally held in adjustment by a spring 36. A vertical passage 38 leads from the chamber 34 to a slanted outlet 39 into a conduit 40 where all the idle air enters except that small amount that comes in the bleed 25. The valve 33 enables adjustment of the ratio of idle air and idle fuel by controlling the amount of idle fuel (in a rich mixture of idle fuel and the little air admitted by the bleed admitted to the conduit 40. Fuelfree air enters the engine through the conduit 40, which may get its fuel-free fuel to idle the engine from the ,air cleaner 41 through a tube 42. The air cleaner 41 also serves to clean the air going to the intake to carburetor 10.

The idle speed of the engine is controlled by an engine idle screw valve 43 which projects out from the opposite side of the carburetor passage 44 and in line with the conduit 40. A conical head 45 projects into the outlet 46 from the conduit may have a flared portion 47 being shaped to deflect the mixture of idle fuel air into the center of the main passage or throat 44 below the butterfly throttle 14. This mixing of the rich idle fuel in entering the conduit 40 through the orifice 39 and controlled by the flared valve 43 gives improved idle mixture compared to spilling air around a cracked throttle with the idle fuel or rich fuel and air past the usual idle needle valve and idle orifice below said cracked throttle. The engine idle valve 43 is controlled by a knurled end 48 and can be held in adjustment by a spring 49. This adjustment screw 48 controls the volume of flow past the cone and flair 46 to control the engine idle speed. Idle speed can also be controlled or affected by retarding the spark timing at closed throttle idle conditions by various means one of which is shown in US. Patent No. 3,162,184, entitled Spark Timing Control, issued Dec. 22, 1964, to applicant.

A sandwich 50 may be mounted between the carburetor 10 and the intake manifold 8 of the engine 9. Gaskets 51 and 52 may be mounted one on each side of the sandwich 50 and held down by cap screws and nuts 53 in the conventional manner.

The idle fuel is shut off by a mechanism and circuit shown in all figures. This involves a speed sensing motor A which includes a large diaphragm 55 ,and a small diaphragm 56 mounted in a housing 57, 58 connected to a valve 60. The valve 60 includes a plug section 61 and a double spool valve 62. A line 63 leads from the engine manifold 8 to a port 64 in the valve. A port 65 leads to a line 66 which goes to a throttle valve structure B and then by a line 67 to a diaphragm-operated idle-tfuel shutoff unit C. A spring 68 urges the valve 62 against a seat 69 towards the diaphragms 55 and 56.

When the pressure from a Pitot tube 70 in a water pump 71 acts on the diaphragm 55 and exerts a force exceeding the pressure in the spring 68 (reduced by the pressure on the diaphragm 56), the valve 62 will move from the position shown in FIG. 6 to a position where the other end of the valve 62 abuts against a seat 72 to close off communication to a bleed 73 and to admit suction from the intake manifold through line 63 past the valve 62.

Throttle valve B is actuated by a throttle arm 75 mounted on the throttle shaft 15 or by actuating rod 76 for anti-percolator valve 77 as shown in FIGS. 1 and 2. Valve B has actuating stem 80 that actuates a double faced valve 81 which is urged to the left in FIG. 6 by a spring 82. The spring 82 is adjusted by an adjustment screw 83. The spring pressure necessary to close the valve 81 against a seat 84 is very light, as suction from the line 66 tends to close valve 81 against that seat 84. When the valves 62 and 81 are moved fully to the right, when viewed as in FIG. 6, they shut off communication to the bleeds 73 and 85 and admit full manifold suction through the lines 66 and 67 and a passage 86 in the idle fuel shut off unit C to the under side of a diaphragm .87 so that it will overcome the pressure of a spring 88 to cause the valve 26 or 26 to shut off the idle fuel either to an idle orifice 89 of FIG. 6 or from the passage 24 to the passage 30, as shown in FIGS. 1 through 5. A spring 90 may hold the valve C in adjustment when the valve C is rotated partially on its threads to give a limited opening to the valve 26 when the line 67 is opened to the atmosphere through bleeds 77 or 85 as controlled b valves A and B.

Whenever the throttle shaft 15 and butterfly 14 are open, the stem 80 and valve 81 will move so that the valve 81 seats on seat 84 shutting off the suction from line 66 to the line 67 and to the under side of the diaphragm 87. Simultaneously, the valve 81 will open communication between the line 67 and the bleed 85 so that atmospheric pressure will be admitted to the under side of the diaphragm 87, and the spring 88 will open the valve 26 to admit fuel through the idle port 89 (or as viewed in FIGS. 4 and 5 open communication between passages 24 and 30). In order to open the valve 26, as shown in FIGS. 4 and 5, the distance between the valve 26 and the stop on the housing of valve C, more movement of valve 26 will have to be provided than for valve 26a when there is no suction on the diaphragm 87 of the valve C. When the engine speed is about above 1000 r.p.m. and the throttle is closed as in high speed decelerations, the pressure from the Pitot tube 70 will move the diaphragm 55 to the right, as viewed in FIG. 6, so that the right hand seat of the valve 62 will abut against the seat 72 closing off communication to the bleed 73. When in this position, suction from the intake manifold flows through the line 63 past the valve 62, through the line 66, past the valve 81 (if the throttle is closed), through the line 67 to the under side of the diaphragm 87, to close off the fuel to idle.

It has already been explained that when the throttle is opened, the suction will not flow past the valve 81, and the bleed 85 will admit atmosphere to the under side of the diaphragm 87, so that the valve 26 will open and turn on the idle fuel to assist acceleration or cruise performance. When the engine speed drops below 1000 i the spring 68 will urge the diaphrag-rns 55 and 56 to the left, so that the left hand face of the valve 62 will abut agiinst the seat 69 to close off suction from the line 63 and open the bleed 73 to the line 66. By this construction, whenever the throttle is closed and the engine speed is above 1000 r.p.m. (such as when decelerating at higher speeds), the diaphragm 87 will cause the valve 26 to close off the idle fuel. As the engine speed is reduced with the throttle closed, such as when getting below 30 mph with an automatic transmission, the diaphragm 55 will move to the left and close off communication between the suction in line 63, past valve 84, and the line 66, and open communication between the lines 66 and 67 and the bleed 73, which returns atmospheric pressure to the under side of diaphragm 87 so that the idle fuel is turned on to keep the engine from stalling. If during a high speed deceleration the throttle is suddenly opened, the valve 81 will close on the seat 84 shutting off suction to line 67 and opening the bleed 85 so that the idle fuel will be turned on as is needed for power or acceleration from high or low speeds.

Pressure from the intake of the water pump 71 is communicated to the enclosure 90 between the diaphragms 55 and 56 by a line 91 in speed-sensing mechanism A. Intake line 92 to the pump 71 is communicated to the bottom of radiator R. Outlet pipe 93 of the pump 71 goes through the engine 9 to the top tank of the radiator R by line or hose 94. As the engine and the water in the radiator R heats up, pressure cap 95 limits such pressure to around 7 to 15 lbs. p.s.i. Because of the pressure distributed through the line 91 from the intake to the pump, line 96 from the Pitot tube 70, each acting on a different side of diaphragm 55, the pressure resulting from high temperatures as controlled by the radiator cap 95 will act equally on both sides of the large diaphragm 55 while only acting on the side of the small diaphragm 56 towards diaphragm 55. Thus, the pressure build up due to the temperature of the cooling liquid as limited by the pressure cap 95 acts on the diaphragm 56 against the action of the spring 68 so that the shift of the valve 62 from the left where the suction from the line 63 is closed ofl? to the right where suction from the line 63 is admitted from the line 66 will occur at a lower speed of the engine at high temperatures and water pressure (due to pressure cap 95) than at cold engine low radiator pressure operations.

When the engine is cold, and there is no pressure under the radiator pressure cap, it may be desirable to turn on the idle fuel during closed throttle decelerations as the engine speed drops to about 1100 to 1400 rpm. but when the engine is hot or quite warm it may be desirable to turn it on at lower speeds as at 1000 or over 9000 rpm. When the engine is much warmer the tendency to stall is reduced and the idle fuel can be turned on at lower speeds without stalling. This automatic differential in the actuation of the speed senser is possible due to this double diaphragm.

The double diaphragm 55, 56 also has the advantage of eliminating the necessity of using a stufiing box with its tendency to stick sometimes when operating in a dirty corrosive liquid such as radiator coolants.

To provide a snap action, a ball 97 acts on one groove at a time of two grooves 98 and 99 in the plug 61 so that enough pressure must be generated on one side of diaphragm 55 to overcome the action of the ball 97 in moving from groove 98 to groove 99 plus the resistance of the spring 68 minus the pressure on diaphragm 56 so that valve 62 will have a snap action from the position of seating on the seat 69 to close ofl? suction from the line 63 to line 66 and open communication to port bleed 73 to the other position of seating on the seat 72 which closes otf the bleed 73 and opens the flow of suction from lines 63 to 66.

A switch 109, with a feeler wire 101 passes through air bleed hole 103 in actuator A, can operate an indicator light by wires 102 if such an indicator is desired. This will show visually when the idle fuel is on or off for test purposes, etc.

I have illustraed my invention in these various forms; however, many other variations may be possible within the scope of this invention.

To those skilled in the art to which this invention relates many changes in construction and widely dilfering embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and description herein are purely illustrative and are not intended to be in any sense limiting.

I claim as my invention:

1. A carburetor for an internal combustion engine having an intake manifold, a throttle means and engine-speed sensing means, comprising means providing a main passage for fuel and air through said carburetor, a throttle valve in said main passage operated by said throttle means, means providing a by-pass for rich air and fuel to idle around said throttle valve and entering said main passage on the intake manifold side of said throttle valve, a richair-and-fuel control valve in said bypass passage for stopping the flow of rich fuel and air therethrough, a motor for actuating said valve, a first combination suction-flow-control and bleed-control valve, a second combination suction-fiow-control and bleed-control valve, said combination valves acting together to control said motor, by being connected in series to control flow from said intake manifold to said motor, said first combination valve being actuated by said throttle means to open its suction-fioW-control valve and close its bleed valve, said second combination valve being controlled by said enginespeed sensing means to open its suction flow control valve and close its bleed valve when said engine speed is above a predetermined speed, whereby said rich-air-and-fuel control valve will substantially stop the flow of rich air and fuel through said bypass passage when said engine is operating at high speeds with the throttle closed, suction from said intake manifold being controlled by said com- 6 bination valves to said motor to accomplish this operation.

2. A carburetor for an internal combustion engine, said carburetor having a main fuel and air passage therethrough, a throttle valve in said passage, a rich fuel and air passage in said carburetor conducting rich fuel and air around said throttle valve, a conduit to supply air to idle said engine, means in said carburetor for mixing said air to idle with said rich fuel and air and delivering said mixed fuel and air in a desirable ratio for idling into said main passage on the engine side of said throttle valve, said mixed fuel and air to idle being delivered to said main passage through a tube extending radially thereunto and having a third control valve, said third valve controlling the rate of flow of said air and fuel to idle and therefore the engine speed at idle, said third control valve extending into said main passage from the diametrically opposite side of said main passage from said tube and extending partly into said tube, whereby said mixed air and fuel to idle enters from one side of said main passage and said control valve is operated from the opposite side of said main passage to provide an exterior adjustment from the outside of said carburetor to adjust the engine idle speed while said throttle valve is essentially closed.

3. A carburetor for an internal combustion engine, said carburetor having a main fuel and air passage therethrough, a throttle valve in said passage, a rich fuel and air passage in said carburetor conducting rich fuel and air around said throttle valve, a conduit to supply air to idle said engine, means in said carburetor for mixing said air to idle with said rich fuel and air and delivering said mixed fuel and air in a desirable ratio for idling into said main passage on the engine side of said throttle valve, a second valve for controlling the fiow of rich fuel and air around said throttle valve, an engine speed sensing device, means controlled by the position of said throttle valve and said speed sensing device for operating said second flow controlling valve so that fuel to idle is substantially cut off when operating said engine at high speed decelerations with a closed throttle, and a first suction-flow-control valve operated by said engine-speed-sensing device, a second suction-flow-control valve operated by said throttle valve, and means for causing said first and second valves to act cooperatively to substantially shut off said fuel to idle when operating at high engine speed decelerations With a closed throttle and turning on said fuel to idle while operating at closed throttle when said engine speed drops below a predetermined speed, to resist or prevent engine stall.

4. A carburetor having a main air passage therethrough, a throttle valve in said passage, a passage for fuel to idle said engine, an engine-speed-sensing first device, a second device actuated by the motion of said throttle valve, a second valve controlling the flow of fuel to idle through said passage, said first and second devices cooperating to control said second valve so that in one position of said second valve said fuel to idle is free to flow in the engine idling system and in the other position of said valve the flow of fuel to idle is substantially cut ofl said first and second devices both being mounted on and supported by said carburetor, said first device includes a suction-flow-control valve, said second device includes a suction-fioW-control valve, and a conduit from the main air passage on the engine side of said throttle that passes through said valves in said first and second devices and controls said second valve, whereby the flow of fuel to idle is controlled as defined herein.

References Cited UNITED STATES PATENTS 1,240,841 9/1917 Gilles 26141 X 1,264,464 4/1918 Weld. 1,691,201 11/1928 Larkin 26141 (Other references on following page) UNITED STATES PATENTS Guthrie 26141 X Mennesson 26141 Chandler 26141 X Messinger 123-124 5 Chisholm 261-41 X Carlson 12397 X Leibing 123214 8 Cornelius. Kane.

Walker et a1. 26141 Arndt 26141 HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner. 

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING AN INTAKE MANIFOLD, A THROTTLE MEANS AND ENGINE-SPEED SENSING MEANS, COMPRISING MEANS PROVIDING A MAIN PASSAGE FOR FUEL AND AIR THROUGH SAID CARBURETOR, A THROTTLE VALVE IN SAID MAIN PASSAGE OPERATED BY SAID THROTTLE MEANS, MEANS PROVIDING A BY-PASS FOR RICH AIR AND FUEL TO IDLE AROUND SAID THROTTLE VALVE AND ENTERING SAID MAIN PASSAGE ON THE INTAKE MANIFOLD SIDE OF THE THROTTLE VALVE, A RICHAIR-AND-FUEL CONTROL VALVE IN SAID BYPASS PASSAGE FOR STOPPING THE FLOW OF RICH FUEL AND AIR THERETHROUGH, A MOTOR FOR ACTUATING SAID VALVE, A FIRST COMBINATION SUCTION-FLOW-CONTROL AND BLEED-CONTROL VALVE, A SECOND COMBINATION SUCTION-FLOW-CONTROL AND BLEED-CONTROL VALVE, SAID COMBINATION VALVES ACTING TOGETHER TO CONTROL SAID MOTOR, BY BEING CONNECTED IN SERIES TO CONTROL FLOW FROM SAID INTAKE MANIFOLD TO SAID MOTOR, SAID FIRST COMBINATION VALVE BEING ACTUATED BY SAID THROTTLE MEANS TO OPEN ITS SUCTION-FLOW-CONTROL VALVE AND CLOSE ITS BLEED VALVE, SAID SECOND COMBINATION VALVE BEING CONTROLLED BY SAID ENGINESPEED SENSING MEANS TO OPEN ITS SUCTION FLOW CONTROL VALVE AND CLOSE ITS BLEED VALVE WHEN SAID ENGINE SPEED IS ABOVE A PREDETERMINED SPEED, WHEREBY SAID RICH-AIR-AND-FUEL CONTROL VALVE WILL SUBSTANTIALLY STOP THE FLOW OF RICH AIR AND FUEL THROUGH SAID BYPASS PASSAGE WHEN SAID ENGINE IS OPERATING AT HIGH SPEEDS WITH THE THROTTLE CLOSED, SUCTION FROM SAID INTAKE MANIFOLD BEING CONTROLLED BY SAID COMBINATION VALVES TO SAID MOTOR TO ACCOMPLISH THIS OPERATION.
 2. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE, SAID CARBURETOR HAVING A MAIN FUEL AND AIR PASSAGE THERETHROUGH, A THROTTLE VALVE IN SAID PASSAGE, RICH FUEL AND AIR PASSAGE IN SAID CARBURETOR CONDUCTING RICH FUEL AND AIR AROUND SAID THROTTLE VALVE, A CONDUIT TO SUPPLY AIR TO IDLE SAID ENGINE, MEANS IN SAID CARBURETOR FOR MIXING SAID AIR TO IDLE WITH SAID RICH FUEL AND AIR AND DELIVERING SAID MIXED FUEL AND AIR IN A DESIRABLE RATIO FOR IDLING INTO SAID MAIN PASSAGE ON THE ENGINE SIDE OF SAID THROTTLE VALVE, SAID MIXED FUEL AND AIR TO IDLE BEING DELIVERED TO SAID MAIN PASSAGE THROUGH THE TUBE EXTENDING RADIALLY THEREUNTO AND HAVING A THIRD CONTROL VALVE, SAID THIRD VALVE CONTROLLING THE RATE OF FLOW OF SAID AIR AND FUEL TO IDLE AND THEREFORE THE ENGINE SPEED AT IDLE, SAID THIRD CONTROL VALVE EXTENDING INTO SAID MAIN PASSAGE FROM THE DIAMETRICALLY OPPOSITE SIDE OF SAID MAIN PASSAGE FROM SAID TUBE AND EXTENDING PARTLY INTO SAID TUBE, WHEREBY SAID MIXED AIR AND FUEL TO IDLE ENTERS FROM ONE SIDE OF SAID MAIN PASSAGE AND SAID CONTROL VALVE IS OPERATED FROM THE OPPOSITE SIDE OF SAID MAIN PASSAGE TO PROVIDE AN EXTERIOR ADJUSTMENT FROM THE OUTSIDE OF SAID CARBURETOR TO ADJUST THE ENGINE IDLE SPEED WHILE SAID THROTTLE VALVE IS ESSENTIALLY CLOSED. 